Research On Transmission Properties Of A Surface Plasmonic Waveguide With Gain Medium

In recent years, much effort has been dedicated to controlling light propagation onnanoscale using surface plasmons (SPs). This conventional diffraction limit can besignificantly reduced using SPs, which are excited state of evanescent waves confined tothe interface of metal-dielectric materials. Through the subwavelength structuremodulation in the surface, it can control the propagation of light actively. The surfaceplasmon waveguides (SPWs) on SPs have been attracted considerable attention due totheir ability of allowing for waveguiding in subwavelength scale. Compared with otherwaveguides, metal-dielectric-metal (MDM) plasmon waveguides are considered to haveunique advantages and easier to be integrated into optical circuits. The bottleneck problemthat impacts the extensive application of MDM waveguide structure is that thepropagation loss in the structure is still large. Thus, a suitable optical gain medium isneeded to compensate for propagation loss. On the basis of these reasons, we investigatethe transmission properties of SPs propagating in a MSM waveguide filled with II-VIgroup semiconductor ZnO as gain medium.The primary work includes the following aspects:(1) The basic properties of SPs are first introduced in this thesis, which focuses on theMDM surface plasmon waveguide and its dispersion relation, propagation constant and soon. The basic properties of MDM waveguide provide some thinking about the design ofnovel structure of light. On the basis of MDM dispersion relation and propagationconstant rules, we design a metal-semiconductor-metal (MSM) plasmonic waveguidestructure embedded with semiconductor gain medium.(2) The dependences of propagation loss and effective refractive index on thegeometrical parameters of the waveguide structure are analyzed using the finite differencetime-domain (FDTD) method. Additionally, the condition for lossless propagation in usingII-Ⅵ semiconductor ZnO as the gain medium is investigated. The simulation results showthat lossless gain-assisted SPs propagation in MSM can be achieved for ultravioletwavelengths when the width of the semiconductor core is80nm or wider.(3) To further study the transmission properties of a surface plasmonic waveguidewith gain medium, we investigate a kind of MSM waveguide with double parallelcylindrical nanorods, and then stimulate it numerically by FDTD. Results show that with the incident light perpendicular to the major axis, the electromagnetic field is wellconfined to the dielectric layer and the intermediate region formed by the two cylindricalnanorods, so the filed can be efficiently coupled into the waveguide. In short, adjusting thegeometrical parameters can significantly improve the confinement of the SPs fields andreduce the losses of the waveguide, so that the effective refractive index and propagationlength of the waveguide can be optimized. Subwavelength optical confinement can beachieved in this kind of plasmonic waveguide, which will be applied to the research ofoptical integration chips and sensors.